Efficient Shuffling of Mobile Drive Units for Inventory Holders

1. A method comprising: positioning multiple inventory holders at corresponding multiple locations at a pick station of an inventory system, the multiple locations including a primary set of multiple pick locations and a secondary set of multiple staging locations; shuffling the inventory holders among the multiple pick locations and the multiple staging locations at the pick station using one or more mobile drive units, the shuffling comprising: retrieving a new inventory holder and depositing the new inventory holder in a first staging location of the multiple staging locations; repositioning a recently-completed inventory holder from a first pick location of the multiple pick locations to a second staging location of the multiple staging locations; repositioning a next inventory holder from a second pick location of the multiple pick locations to the first pick location vacated by the repositioning of the recently-completed inventory holder; repositioning the new inventory holder from the first staging location of the multiple staging locations to the second pick location of the multiple pick locations; and transferring the recently-completed inventory holder away from the second staging location to remove the recently-completed inventory holder from the pick station.

2. The method as recited in claim 1 , wherein the shuffling is performed by a single mobile drive unit.

3. The method as recited in claim 1 , wherein the shuffling is performed by multiple mobile drive units such that a first mobile drive unit performs at least one of the retrieving of the new inventory holder or the transferring of the recently-completed inventory holder and a second mobile drive unit performs the repositioning of the inventory holders among the multiple pick locations.

4. The method as recited in claim 1 , wherein the multiple pick locations are prioritized such that the first pick location is proximally closest to a picker and the second pick location is adjacent to the first pick location.

5. The method as recited in claim 1 , wherein one or more additional inventory holders reside at one or more other pick locations of the multiple pick locations, wherein the shuffling further comprises repositioning each additional inventory holder from a current pick location to an adjacent pick location to sequentially move the one or more additional inventory holders closer to the first pick location, leaving a last pick location vacant, and repositioning the new inventory holder from the first staging location of the multiple staging locations to the last pick location of the multiple pick locations.

6. The method as recited in claim 1 , wherein one or more additional inventory holders reside at one or more other pick locations of the multiple pick locations to form a queue, wherein the shuffling further comprises repositioning the new inventory holder from the first staging location of the multiple staging locations to a pick location of the multiple pick locations that is ahead of at least one other inventory holder already residing in a pick location so that the new inventory holder is higher in the queue than said at least one other inventory holder.

7. A method comprising: retrieving a new inventory holder from a storage location and temporarily placing the new inventory holder in a temporary staging location; moving a mobile drive unit to a first pick location at which a first inventory holder is positioned; repositioning, using the mobile drive unit, the first inventory holder from the first pick location to the temporary staging location proximal to the first pick location upon the first inventory holder being recently completed; repositioning, using the mobile drive unit, a second inventory holder from a second pick location to the first pick location vacated by the repositioning of the first inventory holder, the second pick location being located adjacent to the first pick location; transporting, using the mobile drive unit or another mobile drive unit, the first inventory holder away from the temporary staging location; and repositioning, using the mobile drive unit, the new inventory holder from the temporary staging location to one of the second pick location or a third pick location, wherein the temporary staging location and the first, second and third pick locations are part of a pick station within a warehouse.

8. The method as recited in claim 7 , wherein the first inventory holder is repositioned to the temporary staging location for a temporary period of time such that the transporting of the first inventory holder away from the temporary staging location is initiated no later than upon completion of the positioning of the second inventory holder into the first pick location.

9. The method as recited in claim 7 , further comprising repositioning, using the mobile drive unit, a third inventory holder to the second pick location vacated by the repositioning of the second inventory holder.

10. The method as recited in claim 7 , further comprising: repositioning, using the mobile drive unit, a third inventory holder from a third pick location to the second pick location vacated by the repositioning of the second inventory holder; and subsequently repositioning, using the mobile drive unit, the new inventory holder from the temporary staging location to the third pick location vacated by the third inventory holder.

11. The method as recited in claim 7 , further comprising initially repositioning, prior to the moving of the mobile drive unit to the first pick location, the second inventory holder from an original location to a temporary location to clear a path to the first pick location for the mobile drive unit.

12. The method as recited in claim 7 , further comprising initially retrieving the second inventory holder and temporarily positioning the second inventory holder in a staging location while the mobile drive unit repositions the first inventory holder from the first pick location to the temporary staging location.

13. An inventory system comprising: a plurality of mobile drive units that are remotely controllable to transport inventory holders about a warehouse; and a management module configured to direct movement of the plurality of mobile drive units to transport the inventory holders among regions in the warehouse, the management module being further configured to direct a mobile drive unit from the plurality of mobile drive units to perform a shuffle process within a region of the warehouse as follows: directing the mobile drive unit or another mobile drive unit from the plurality of mobile drive units to retrieve a new inventory holder from a storage location and temporarily placing the new inventory holder in a temporary staging location; directing the mobile drive unit to reposition a first inventory holder from a first pick location within the region to the temporary staging location within the region that is proximal to the first pick location upon the first inventory holder attaining a completion status; directing the mobile drive unit to subsequently position a second inventory holder from a second pick location into the first pick location vacated by repositioning the first inventory holder, the second pick location being adjacent to the first pick location; directing the mobile drive unit or another mobile drive unit from the plurality of mobile drive units to transport the first inventory holder away from the temporary staging location within the region of the warehouse; and directing the mobile drive unit or another mobile drive unit from the plurality of mobile drive units to reposition the new inventory holder from the temporary staging location to the second pick location or a third pick location, wherein the region of the warehouse includes a pick station.

14. The inventory system as recited in claim 13 , wherein the management module is further configured to direct the mobile drive unit to initially place the second inventory holder in a temporary location while the mobile drive unit subsequently repositions the first inventory holder from the first pick location to the temporary staging location.

15. The inventory system as recited in claim 13 , wherein the management module is further configured to direct the mobile drive unit to initially move the second inventory holder from an original location to a temporary location to clear a path to the first pick location for the mobile drive unit.

16. The inventory system as recited in claim 13 , wherein the management module is further configured to direct the mobile drive unit or said another mobile drive unit to initially retrieve the second inventory holder from another region of the warehouse and temporarily position the second inventory holder in a temporary location while the mobile drive unit repositions the first inventory holder from the first pick location to the temporary staging location.

17. An inventory system comprising: a plurality of inventory holders to store items, the plurality of inventory holders including at least first, second, and third inventory holders wherein the first inventory holder is positioned at a first pick location of a pick station, the second inventory holder is positioned at a second pick location of the pick station, and the third inventory holder is positioned at a third pick location of the pick station; and a mobile drive unit configured to shuffle the first, second, and third inventory holders as follows: retrieving a new inventory holder and depositing the new inventory holder in a first holding location; moving the first inventory holder from the first pick location to a second holding location upon the first inventory holder attaining a complete status, the second holding location being separate from the first, second, and third pick locations, the first and second holding locations being located adjacent to each other and separate from the first, second, and third pick locations; subsequently moving the second inventory holder from the second pick location into the first pick location vacated by the first inventory holder; and subsequently moving the third inventory holder from the third pick location into the second pick location vacated by the second inventory holder; and subsequently moving the first inventory holder away from the second holding location to remove the first inventory holder from the pick station, wherein the first and second holding locations are located within the pick station.

18. The inventory system as recited in claim 17 , wherein the mobile drive unit is further configured to subsequently move a fourth inventory holder from the plurality of inventory holders into the third pick location vacated by the third inventory holder.

19. The inventory system as recited in claim 17 , wherein the mobile drive unit is a first mobile drive unit and further comprising: a second mobile drive unit configured to relieve the first mobile drive unit from bringing the new inventory holder to the pick station and moving the first inventory holder from the second holding location to another region separate from the pick station.

20. The inventory system as recited in claim 19 , further comprising a management module to send instructions to the first and second mobile drive units to coordinate movement of the first and second mobile drive units.